1. Field of the Invention
The present invention relates to a stator support structure. More specifically, the present invention relates to a stator support structure of a torque converter for fixing a stator to a stationary shaft and carrying it on an impeller hub and a turbine hub.
2. Background Information
A torque converter is a fluid coupling mechanism that transmits torque between the crankshaft of an engine and the input shaft of an automatic transmission. A torque converter typically has three types of runners (impeller, turbine, stator) located inside for transmitting the torque by means of an internal hydraulic oil or fluid. The impeller is fixedly coupled to the front cover that receives the input torque from the crankshaft of an engine. The hydraulic chamber formed by the impeller shell and the front cover is filled with hydraulic oil or fluid. The turbine is disposed opposite the front cover in the hydraulic chamber. When the front cover and the impeller rotate together, the hydraulic oil flows from the impeller to the turbine, and the turbine rotates. As a result, the torque is transmitted from the turbine to the main drive shaft of the transmission.
The stator regulates the direction of liquid flowing from the turbine toward the impeller. Thereby, a large torque ratio is obtained when the impeller rotates fast and the turbine rotates slowly, and the torque ratio decreases as a difference between the rotation speeds of them decreases.
In general, the stator is formed of a stator carrier of a disk-like form and a plurality of blades fixed to the outer periphery of the stator carrier. Before the rotation speed of the turbine approaches the rotation speed of the impeller, the fluid collides with concave surfaces of the blades of the stator. In this state, rotation of the stator is inhibited. When the rotation speed of the turbine increases, the fluid starts to collide with rear surfaces, i.e., convex surfaces of the blades so that the flow of fluid changes to increase the resistance. Therefore, the rotation of the stator is allowed to eliminate the resistance.
A one-way clutch is used for selectively inhibiting and allowing the rotation of the stator depending on the direction of the fluid flow.
The one-way clutch in the prior art is generally formed of a first race or support member coupled to a stationary shaft, a second race or support member fixed by press-fitting or the like to an inner periphery of a stator carrier, and engagement members such as ratchet claws, rollers or the like disposed between the first and second support members. A retainer is arranged on a side of the one-way clutch for axially positioning the one-way clutch and carrying a thrust load. Further, thrust bearings are arranged between a group including these members and a group including the turbine hub and the impeller hub.
The conventional stator support structure including the one-way clutch is formed of many components, and particularly it is difficult to reduce the axial size of the torque converter. In Japanese Laid-Open Patent Publication Nos. 5-45306 (1993-45306) and 11-2303 (1999-2303) and others, therefore, such a structure is already proposed that a pair of axially opposed surfaces are formed, and a one-way clutch is arranged between these surfaces.
The structure disclosed in the above publications is likewise configured such that the one-way clutch receives an axial load when it is locked, and therefore a retainer and a thrust bearing must be arranged so that the thrust load generated by the fluid may not act on the one-way clutch. Therefore, the number of parts is not sufficiently reduced. Although the Japanese Laid-Open Patent Publication No. 11-2303 has does not disclose a retainer and thrust bearings, a retainer and thrust bearings are required when attaching the one-way clutch disclosed in this publication to the torque converter.
In view of the above, there exists a need for a stator support structure of a torque converter which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the present invention is to reduce the number of parts in a structure for supporting a stator, and particularly to reduce an axial size of the torque converter.
According to a first aspect of the present invention, a stator support structure for coupling a stator of a torque converter to a stationary shaft and supporting the stator on an impeller hub and a turbine hub includes a first support member, a second support member and a one-way clutch body. The first support member has a first annular flange coupled nonrotatably to the stationary shaft and extending radially outward, and a first thrust receiving portion for receiving a thrust load. The second support member has a second annular flange formed of an inner peripheral portion of the stator extending radially inward and opposed to the first annular flange, and a second thrust receiving portion being in contact with the first thrust receiving portion for receiving the thrust load. The one-way clutch body is disposed between the first and second annular flanges, and is subjected to an axial load in a locked state for inhibiting rotation of the stator only in one direction.
In this stator structure, when a thrust load is applied to the stator as a result of the operation of the torque converter, the thrust load is caused by the contact between the first thrust receiving portion of the first support member and the second thrust receiving portion of the second support member, and is not applied to the one-way clutch body arranged between the first and second support members.
This structure does not require a retainer, which is employed in the prior art. Since the second support member is integrated with the stator, required parts can be small in number. Since the parts are small in number, the axial size of the torque converter can be small.
According to a second aspect of the present invention, the stator support structure of the first aspect of the present invention further includes a pair of thrust bearings each arranged between the first or second support member and corresponding one of the impeller hub and the turbine hub.
In this structure, the thrust load acting on each support member is applied through the thrust bearing to the impeller hub or the turbine hub.
According to a third aspect of the present invention, the stator support structure of the first or second aspect of the present invention further has such a structure that the second annular flange of the second support member is provided with a plurality of circumferentially spaced concavities. The one-way clutch body has a plurality of ratchet claws and a plurality of notches. The ratchet claws are arranged within the concavities of the second annular flange, respectively, and have ends capable of projecting toward and escaping from the first annular flange. The notches are formed on the first annular flange of the first support member, and are engaged with the ratchet claws only in one of the rotating directions, respectively.
In this structure, since the ratchet claws are arranged within the concavities of the second annular flange, a member dedicated to arrangement of the ratchet claws is not required so that required parts can be small in number.
According to a fourth aspect of the present invention, the stator support structure of the third aspect of the present invention further has such a feature that the stator and the second support member are made of resin. In this structure, since the second support member is made of resin, the concavities for arranging the ratchet claws can be easily formed.
According to a fifth aspect of the present invention, a stator support structure for coupling a stator of a torque converter to a stationary shaft and supporting the stator on an impeller hub and a turbine hub includes a first support member, a second support member, a one-way clutch body and a retainer. The first support member has a first annular flange coupled nonrotatably to the stationary shaft and extending radially outward. The second support member has a second annular flange formed of an inner peripheral portion of the stator extending radially inward and opposed to the first annular flange, and a second thrust receiving portion for receiving a thrust load. The one-way clutch body is disposed between the first and second annular flanges, and is subjected to an axial load in a locked state for inhibiting rotation of the stator only in one direction. The retainer is in contact with the thrust receiving portion of the second support member for receiving the thrust load. The stator, the second support member and the retainer are made of resin. The side surface of the second annular flange of the second support member can be in direct contact with one of the inner side surface of the turbine hub and the inner side surface of the impeller hub, and the retainer can be in direct contact with the other of the inner side surface of the turbine hub and the inner side surface of the impeller hub.
In this structure, since the second support member and the retainer are made of resin, these can be in direct contact with the turbine hub and the impeller hub. Therefore, two thrust bearings, which are employed in a conventional structure, are not required so that the parts can be reduced in number, and the axial size can be reduced.
The thrust load, which is caused by the operation of the torque converter, is caused by the thrust receiving portion of the second support member and the retainer, and can be prevented from acting on the one-way clutch body.
According to a sixth aspect of the present invention, the stator support structure of the fifth aspect of the present invention further has such a feature that the retainer is in direct contact with the inner side surface of the impeller hub, and the resin forming the stator and the second support member has lower slidability than the resin forming the retainer.
In the torque converter, the inner side surface of the impeller hub is subjected to a larger thrust load than the inner side surface of the turbine hub. Therefore, the member in direct contact with the inner side surface of the impeller hub must have higher slidability that the member in contact with the inner side surface of the turbine hub. However, the structure, in which the members in contact with the inner side surfaces are made of resin, is expensive if a large amount of resin having high slidability is to be used. Accordingly, the resin having high slidability is used only for the retainer having smaller sizes than the stator and the second support member, resin having lower slidability than the resin of the retainer is used for the stator and the second support member. Thereby, the increase in manufacturing cost of the stator support structure using resin materials can be minimized while keeping intended function of bearing the large thrust load occurred on the impeller hub side.